inspired by a cloudflare diff, cleanse old memory when expanding a bignum.

however, instead of trying to audit all the places where a secret bignum
is used, apply the big hammer and clear all bignums when freed.
ok deraadt miod

2 files changed, 18 insertions, 34 deletions

diff --git a/src/lib/libcrypto/bn/bn_lib.c b/src/lib/libcrypto/bn/bn_lib.c
index 9787a31dbb..a8022f6668 100644
--- a/src/lib/libcrypto/bn/bn_lib.c
+++ b/src/lib/libcrypto/bn/bn_lib.c
@@ -226,22 +226,11 @@ void BN_clear_free(BIGNUM *a)
                 free(a);
         }
 
-void BN_free(BIGNUM *a)
-        {
-        if (a == NULL) return;
-        bn_check_top(a);
-        if ((a->d != NULL) && !(BN_get_flags(a,BN_FLG_STATIC_DATA)))
-                free(a->d);
-        if (a->flags & BN_FLG_MALLOCED)
-                free(a);
-        else
-                {
-#ifndef OPENSSL_NO_DEPRECATED
-                a->flags|=BN_FLG_FREE;
-#endif
-                a->d = NULL;
-                }
-        }
+void
+BN_free(BIGNUM *a)
+{
+        BN_clear_free(a);
+}
 
 void BN_init(BIGNUM *a)
         {
@@ -400,7 +389,10 @@ BIGNUM *bn_expand2(BIGNUM *b, int words)
                 {
                 BN_ULONG *a = bn_expand_internal(b, words);
                 if(!a) return NULL;
-                if(b->d) free(b->d);
+                if(b->d) {
+                        OPENSSL_cleanse(b->d, b->dmax * sizeof(b->d[0]));
+                        free(b->d);
+                }
                 b->d=a;
                 b->dmax=words;
                 }
diff --git a/src/lib/libssl/src/crypto/bn/bn_lib.c b/src/lib/libssl/src/crypto/bn/bn_lib.c
index 9787a31dbb..a8022f6668 100644
--- a/src/lib/libssl/src/crypto/bn/bn_lib.c
+++ b/src/lib/libssl/src/crypto/bn/bn_lib.c
@@ -226,22 +226,11 @@ void BN_clear_free(BIGNUM *a)
                 free(a);
         }
 
-void BN_free(BIGNUM *a)
-        {
-        if (a == NULL) return;
-        bn_check_top(a);
-        if ((a->d != NULL) && !(BN_get_flags(a,BN_FLG_STATIC_DATA)))
-                free(a->d);
-        if (a->flags & BN_FLG_MALLOCED)
-                free(a);
-        else
-                {
-#ifndef OPENSSL_NO_DEPRECATED
-                a->flags|=BN_FLG_FREE;
-#endif
-                a->d = NULL;
-                }
-        }
+void
+BN_free(BIGNUM *a)
+{
+        BN_clear_free(a);
+}
 
 void BN_init(BIGNUM *a)
         {
@@ -400,7 +389,10 @@ BIGNUM *bn_expand2(BIGNUM *b, int words)
                 {
                 BN_ULONG *a = bn_expand_internal(b, words);
                 if(!a) return NULL;
-                if(b->d) free(b->d);
+                if(b->d) {
+                        OPENSSL_cleanse(b->d, b->dmax * sizeof(b->d[0]));
+                        free(b->d);
+                }
                 b->d=a;
                 b->dmax=words;
                 }